Shaky, jerky eyes in an 8-week-old infant

Samuel, an 8-week-old infant, presents to primary care with bilateral “shaky, jerky eyes.” The child had been developing normally but was observed by his mother to have “shaky, jerky eyes” when his eyes were opened.

History

Samuel was delivered via c-section at a gestational age of 38 weeks to multi-racial parents. His mother was of Asian descent, and his father was Dutch/German. There was no known family history of genetic disorders. He weighed 8 lbs 4 oz. The delivery was uncomplicated, and Samuel passed all his newborn screening tests. He had no signs of developmental delays and was adequately gaining weight after delivery.

Physical examination

When Samuel presented at 8 weeks, his vital signs were all within normal limits:

Temperature: 98° F

Weight: 15.7 lbs

Pulse: 140 beats per minute

Respiratory rate: 36 breaths per minute

Head circumference: 38 cm

In general, he was alert, well-nourished, well-developed, and was in no acute distress. He cooed during examination and had a social smile. He became upset with the examination but was easily calmed by his parents.

Abdomen: bowel sounds positive in all 4 quadrants, soft, no tenderness, no hepatosplenomegaly.

Neuro: face was symmetric. Strong sucking and rooting reflex. No muscle atrophy; he was able to move all extremities equally; normal tone; reflexes 2+ at patella, ankle, and biceps bilaterally; there was no head bobbing; tonic neck reflex was intact and symmetric.

Apart from the bilateral pendular nystagmus, Samuel's physical examination was unremarkable. Nystagmus in an infant can represent both normal physiology and an alarming symptom for an underlying serious, but rare, disease. Though the majority of cases of nystagmus are considered congenital or infantile, 20% of nystagmus cases are acquired and require a full neurological workup.1 Infantile nystagmus occurs in the first 3 to 6 months of life, and acquired nystagmus develops after 6 months of life.2 Differentials for nystagmus in childhood vary from idiopathic, to ocular, and neurologic disorders (see Table 1).2 Therefore, primary care clinicians need to recognize and refer promptly if infantile nystagmus is observed, as it may be a symptom of a serious underlying disorder or a rare genetic disorder.

Evaluation and testing

Samuel was referred urgently to pediatric ophthalmology and pediatric neurology. Due to timing, he saw the ophthalmologist initially and was scheduled for an urgent MRI. His brain MRI was unremarkable and showed no evidence of cerebellar lesions. As a result, Samuel was diagnosed with congenital nystagmus and subsequently evaluated by a neurologist with recommendations to follow up in 1 month. At the 6-month well-child visit, the parents shared that they noticed that Samuel would always squint when exposed to any normal or bright light conditions. Samuel was reevaluated by the pediatric ophthalmologist, who discussed the possibility of a diagnosis of achromatopsia. Thus, Samuel was referred to a retina specialist for evaluation, diagnosis, and treatment recommendations.

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